Pump



Feb. 3, 19.59 J. ZIMMERMAN 2,871,846

' Pum3` v v Filed Dec'. 27, 1955 2 sheets-sheet 1 ATTORN EY Feb. 3, 1959J. Z'IMMERMAN l 2,871,846

` PUMP Filed Dec. 27,1955

2 Sheets-Sheet 2 INVENTOR (f2/? Erf/wmf? aww ATTORNEY United StatesPatent O i PUMP John Zimmerman, Grosse Pointe Woods, Mich., assignor toGeneral MotorsCorporation, Detroit, Mich., a corporation of DelawareApplication December 27, 1955, Serial No. 555,582 2 Claims. ('Cl.123-140) The present invention relates to pumps and more particularly tovariable rate, positive displacement pumps.

Under certain conditions it is desirable to employ a positivedisplacement pump which is very compact but which is economical tomanufacture and reliable in operation. As an example, in a fuelinjection system for a spark ignited, internal combustion engine, insome types of injection systems, it is desirable to employ a piston typepump to enable a precision metering of the fuel discharged from thepump. However, heretofore, pumps of this nature have been bulky andexpensive to manufacture and in addition, t'heyhave been diicult tomaintain in operation. When a plunger or piston is reciprocably drivenwithin a cylinder by means of a rotating crankshaft, etc.,it is diicultto maintain the `piston or plunger in axial alignment with the cylinder.This problem is especially acute where an effort is made to decrease thesize of the pump by placing the cylinders and the pistons as close aspossible to the axis of rotation of the rotating drive member. Such anarrangement normally results in a considerable side thrust on the pistonor plunger that in turn results in a strong tendency for the axis of thepiston or plunger to become skew to the axis of the cylinder.

It is now proposed to provide a compact pump which will employ a pistonreciprocably driven in a cylinder by a rotating member and still have alarge capacity for its size. This pump may employ a pair of cylindersdisposed in axial alignment with each other on diametrically oppositesides of a driving eccentric or cam. A yoke may surround the eccentricor cam and be driven thereby with the opposite ends of the yoke formingpistons or plungers that are reciprocably disposed inside the cylindersin axial alignment therewith. Since the opposite ends of the yoke arewidely spaced from each other and they always will be substantiallyconcentric in the cylinders, axial alignment of the pistons will beassured. Thus the pistons may be located very close to the axis ofrotation of the eccentric without resulting in any side thrust ormisalignment. In fact, each of the pistons'may be relatively shortmembers in direct driving engagement with the eccentric or cam at alltimes. In order to further improve the effectiveness of the pump andreduce the cost thereof, a plug of resilient material such as rubber maybe disposed in the cylinder and engaged by the piston. `One end of theplug may have a cavity therein that forms a pumping chamber. Thus thereciprocating movement of the .piston will result in the plug beingperiodically compressed. This periodic compression of the plug willresultin the capacity of the cavity increasing and decreasing therebyproducing a pumping action. The resilient plug will engage the walls ofthe cylinder very tightly and provide a liquid tight seal irrespectiveof any minor irregularities in the surfaces of the piston and/ orcylinder walls.

It is also proposed to provide a variable lift cam for driving the yoke.the stroke of the piston, thereby making it possible to This will makeitpossible to control readily vary the output `of the pump. In thepresent instance this cam comprises a cylindrical sleeve mounted forrotation about an axis that intersects the axis of the cylinder but isoblique thereto. Thus by moving the cylindrical surface in an axialdirection, the amount of life or eccentricity thereof may be varied fromzero to any desired amount, and as a consequence, the stroke of thepistons can be readily adjusted.

In the drawings:

Figure 1 is a vertical cross sectional view of an engine employing afuel injection pump embodying the present invention. Y i

Figure 2 is a horizontal cross sectional view of a pump adapted to beembodied in the fuel injection system employed in Figure l.

Figure 3 is a longitudinal cross sectional view of the pump takensubstantially along the plane of line 3--3 in Figure 2.

Figure 4 is a cross sectional view taken substantially along the planeof line 4-4` in Figure 3.

Figure 5 is an exploded perspective view diagrammati- Y callyillustrating one form of the embodiment of the present invention. l

Figure 6 is an exploded perspective view diagrammatically illustratinganother form of the present invention.

Referring to the drawings in more detail, the present invention may beembodied in a pump suitable for use in a fuel injection system 10 for aninternal combustion engine 11. This engine 11 may be of any desired typesuch as a sof-called V tyue having a cylinder block 12 with a pair ofangularly disposed banks of cylinders 14. These cylinders 14 are chargedthrough intake passages 16 extending through thecylinder heads 18secured to the banks of cylinders. The fuel iniection system 10 mayinclude a fuel metering and/or distributing unit 19 for drawing fuelfrom a source suchas a fuel tank and for metering and/ or distributingthe fuel to the various intake passages 16 to mix with the induction airtherein to form a combustible charge for the cylinders 14.

The metering and/or distributing system 19 may include a pump 20 adaptedfor mounting on a web 22 that extends between the two banks of cylinders14. The present pump 20 includes a housing 24 having a chamber 26 withan upper bearing 28 and a lower bearing 30 disposed on the oppositesides thereof for rotatably supporting a vertical driveshaft 32. Thedriveshaft 32 may project downwardly into the camshaft gallery 34 andhave a gear 36 on the lower end thereof driven by a similar gear 38 onthe camshaft 40. Thus the pump 20 will be driven at some fixed ratio tothe engine speed. l Although the pump 20 may employ any number ofpumping cells 42 and 44, in the present instance it includes a pair ofaxially aligned cylinders 46 and 48 disposed on diametrically oppositesides of the driveshaft 32. In other words the cylinders 46 and 48 willbe symmetrically disposed about the driveshaft 32 with their axes in aplane normal thereto.

A yoke 50 may be provided which has an opening 52 in the center thereofto straddle the driveshaft 32 while the opposite ends 54 and 56 of theyoke 50 are disposed in the cylinders 46 and 48. These ends of the yoke50 are preferably a sliding lit in the cylinders 46 and 48 so that theymay function as pistons. Since each end 54 and 56 of the yoke 50 will bedisposed concentric with the cylinders 46 and 48, the wide spacing ofthe ends 54 and 56 will result in the yokepSt) being retained in exactaxial alignment at all times. Thus if the ends 54 and 56 of the yoke 50`form the pistons or plungers that reciprocate in the cylinders 46 and48, the cylinders may be disposed very close to the cam or eccentric 58.In fact, the Working surfaces of the pistons may be only thethickposedin the central` opening 521 through, the middle of.'

theyoke Sii.v The surface` of the diametrically opposite sidesof thisopening` may engage the opposite sides: of

the eccentric 58; in alignment with the axisof the cylinders 4 6 and48.V This will provide a positive force in both directions of movementof the yoke 50 without producing any lateral thrust that would tend tolforce` the pistonsagainst the sides of the cylinders 46 and 48.- Itshould be notedlthata clearance space 60-on the opposite sides of theopening 52 eliminates any interference between the Vyokeflland eccentricSSL Inserts 62 may bepress tted in a passage through the ends 54 and 56of the yoke 5t) so that a spherical surface 64-thereon will ride ontheeccentric 58; This will provide a point contact between the yoke 50 andeccentric 58.

lt may thus be seen that as the engine camshaft 40 rotates, the gear 38thereon will rotatably drive the vertical driveshaft 32of the pump 20.As the driveshaft 32 and the eccentric 58 thereon rotates, the yoke 5t)vwill reciprocate between the two cylinders 46 and 48 and produce apumping action.

In order to increase the effectivenessV of thispumping action, aresilientplug 66of some suitable material'such as a rubbermay beprovided in each of the cylinders 46 and-48. One end of each plug 66 maybe flat'to engage the end of theyoke 50 while the opposite end oftheplug 66 has acavity 68 formed therein. These cavities'68 cooperate withthe inner ends of the cylinders 46 and 48 to formpumping chambers 70.Inlet 'passages'72 extend through the housing 24v so that an inlet valve74 may bc provided for each of the cylinders 46 and 48. The inletpassages 72 are adapted to draw fuel from suitable' sources such as astorage tank. An outlet passage 76 may be'provided for each cylinder 46and 48l for allowing the fuel tobe pumped into thefuel distributingsystem 19y for discharging the fuel into the various intake passages 16.It is preferable that the inlet passages 72 intersect the bottom of thepumping chamber 70 and that the outlet passages 76 draw fuel from thetop of the chamber 70. Thus if there are any vapors in the chamber. 70,they will collect' adjacent the outlet valve and be vented during everypumping cycle. By maintaining the plugs 66 under compression at alltimes, an effective sealing action will be provided that will preventthe loss of uidvfrom the pumping chamber 70 without undue machining ofthe mating surfaces. `Also wearing of the cylinder surfaces etc. byabrasion from foreign particles in thefluid will not destroy theeffectiveness of the pump.

When the yoke 5t) moves to one side, one of the resilient plugs 66 willexpand andthe other plug 66 will be compressed. This will result in,respectively, an increase and a decrease in the capacities of thechambers 70.`

Thus fuel will be drawn inwardly through the inlet 72` til) the otheroutlet. Thus a positivel pumping action will result that will have anoutput substantially equal to the total swept volume of the pistons orends of the yoke` 50, i. e., the area times the stroke. Thev outputsfrom cach of the cells may be combined to producev aunitary. flow of uidor the outputs may be kept separate.

In order to vary the rate or quantity offfuel discharged from the pump20, the eccentric or cam 5S may have a variable lift whichl is effectivefor varyingthe travel of., the. yoke 5t) and thus the stroke of thep'ump 2 (i`. Thev i present eccentric 58 is a hollow cylindrical sleeve80 mounted on a cylindrical spindle 82 that rotates with the driveshaft32. The axis of the spindle 82 is oblique to the axis of rotation sothat either one or both ends of the spindle 82 are displaced from theaxis while some intermediate portion is concentric with the axis ofrotation. Thus the amount of eccentricity of the sleeve will vary in anaxial direction. Accordingly, by moving the sleeve 80 and spindle 82they eccentricity thereof will vary, thus varying. the. stroke of thepiston and consequently, the output from the pump 20.

Although any suitable control means may be provided for moving thesleeve 80 in an axial direction, in the present instance a pneumatic.system including a spring biased diaphragm 84 isprovided. The balancebetween the spring and the pressure in the plenum chamber 86 willdetermine the axial position of the cam 53 and its surface. As aconsequence, the rate of output of the pump Ztlmay, be determined by theplenumA chamber pressure which is characteristic of the engine fuelrequirements.

Under some circumstances,v ity may be desirable to provide more pumpingcells to allow a separate cell for each engine cylinder, produce a morecontinuous output, and/or increase the capacity of the pump, etc.Accordingly, the pump 20 may be equipped with additional cells. Onemeansof accomplishing this is to provide another pair. of cells that aredisposed inthe same plane as the rst pair of cells but at right anglesthereto. A

separate yoke 100. and 1tl2isprovided for each pair of alignedcylindersso that the opposite ends 104 ofv the yokes 10Q and 102 will bedisposed in the cylinders. Thesecylinders. are preferably substantiallylidentical to eachother and similar inallrespects to the first describedembodiment.

Each of the yokesltll) andl102, as best'seen in Figure 6, has an offsetcenter portion 106 with a central opening 108 therein for the cam oreccentric 110 and a pair of cylin-drical ends 104 that are adapted to tinto the cylinders. The offset center portions 106 will allow the twoyokes 'and1il2 to intermesh with each other with the cylindrical ends104 being disposed in a common plane. Each end of the yokes 100 and 102may have an insert 113 with spherical surfaces thereon that will engagethe surface of the cam 110. It may thus be seen that all of thespherical surfaces will engage the cam along a common plane normal tothe axis of rotation. This insures all of the cells having identicalstrokes at all times even when the cams lift varies in an axialdirection.

It will thus be-seen that a plurality of cells may be provided whilestill employing a compact structure wherein the plungers will always bemaintained in axial alignment.

It is to be understood that, although the invention has been describedwith specific reference to particular embodiments thereof, it is not tobe so limited since changes and alterations therein may be made whichare within the full intended scope of this invention as defined by theappended claims.

I claim:

1. A pump structure comprising a housing having a chamber in the centerthereof, a driveshaft extending longitudinally of said housingzandthrough said chamber, a cam mounted'on said driveshaft and'disposedinside of said chamber, a pair of axially aligned cylinders disposedsubstantially normal to the axis of'said driveshaft with the inner endsthereof opening into diametrically oppositey portionson diametricallyopposite ends thereof disposed;

in the inner ends of.l said cylinders for engaging, said resilientplugs, said plunger portions being a sutiiciently close lit in saidcylinders for maintaining said yoke in axial alignment therewith, saidyoke engaging said cam at points in substantial alignment with the axisof said cylinders for reciprocating said yoke to alternately compresssaid resilient plugs and thereby produce a pumping action in saidpumping chambers.

2. In a fuel injection system for an internal combustion engine, thecombination of a pump housing having a chamber therein, a rotatabledrive shaft extending through said housing and said chamber, a camrotatably driven by said driveshaft and disposed in said chamber, saidcam being axially movable with the amount of lift thereof varying in anaxial direction, aligned cylinders in said housing opening intodiametrically opposite sides of said chamber adjacent said cam, a yokedisposed in said chamber and having plunger portions on diametricallyopposite ends thereof reciprocably disposed in said cylinders tomaintain said yoke in axial alignment therewith, plugs of resilientmaterial disposed in said cylinders to be engaged by said plungerportions to form pumping References Cited in the tile of this patentUNITED STATES PATENTS 2,262,181 Hover Nov. l1, 1941 2,319,566 Sundermanet al May 18, 1943 2,392,117 Burks Jan. 1, 1946 2,393,175 Laskey Jan.15, 1946 2,491,230 Theis Dec. 13, 1949 FOREIGN PATENTS 128,919 SwedenAug. l, 1950

